Mix design testing methods and ground improvement methods
The mix design test method rapidly determines the optimal first addition of solidifying agent by measuring pH transitions, improving unconfined compressive strength and adapting to site-specific ground conditions.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- ONODA CHEM IND CO LTD
- Filing Date
- 2024-12-26
- Publication Date
- 2026-07-08
AI Technical Summary
Existing methods for determining the optimal amount of solidifying agent to be initially mixed with ground material in a two-stage addition process are time-consuming, relying on uniaxial compressive strength measurements or 7-day strength estimates, which are not efficient.
A mix design test method that measures the pH of the soil mixture during staged addition of the solidifying agent, determining the first addition amount based on a characteristic curve where the pH transitions from 10.5 to 12.5, allowing rapid determination of the optimal first addition.
Enables quick and accurate determination of the optimal first addition of solidifying agent, enhancing unconfined compressive strength and adaptability to varying ground conditions.
Smart Images
Figure 2026114673000001_ABST
Abstract
Description
[Technical Field]
[0001] This invention relates to a mix design test method and a ground improvement method using a solidifying agent. [Background technology]
[0002] Conventionally, in methods for solidifying the ground by mixing soil materials and solidifying agents, methods are known that can prevent an increase in the amount of solidifying agent used. For example, Patent Document 1 describes a ground improvement method characterized by adding and mixing a portion of the final amount of solidifying agent to the target improved soil, and then adding and mixing the remaining amount of solidifying agent. This method is said to prevent an increase in the amount of solidifying agent used. [Prior art documents] [Patent Documents]
[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-230821 [Overview of the Initiative] [Problems that the invention aims to solve]
[0004] Incidentally, when performing the above-mentioned phased addition, there is currently no established method for determining the amount to be added in the first addition. One example is to determine it from the uniaxial compressive strength of a mix design test without phased addition. The compressive strength of soil mixed with solidifying agent is defined by the 28-day strength. In addition, the 28-day strength can sometimes be estimated from the 7-day strength. In other words, it takes a considerable amount of time to determine in advance the optimal amount of solidifying agent to be mixed into the ground material.
[0005] Therefore, the present invention aims to provide a mix design test method that can quickly determine the optimal amount of solidifying agent to be initially mixed with the ground material in a ground improvement method in which a solidifying agent is added to the ground material in two stages and mixed. [Means for solving the problem]
[0006] The present invention relates to a test method for determining the amount of the first solidifying agent to be added to a ground improvement method, in which the solidifying agent is added to the ground material in two stages and mixed together.
[0007] The present invention's mixing test method includes: a measurement step of stirring and mixing the ground material and the solidifying agent, and then measuring the pH of the mixed soil of the ground material and the solidifying agent for each of several different amounts of the solidifying agent added to the ground material; and a first addition amount determination step of determining the first addition amount, which corresponds to the point where, when the amount of the solidifying agent added is increased according to a characteristic curve representing the correlation between the amount of the solidifying agent added to the ground material and the pH of the mixed soil, the pH of the mixed soil moves from below a threshold in the range of 10.5 to 12.5 to exceeding that threshold.
[0008] Thus, in the mix design test method of the present invention, the amount of solidifying agent to be added to the ground material for the first time is determined from the pH measurement results of the soil mixture of ground material and solidifying agent. Therefore, the amount of solidifying agent suitable for the first addition to the ground material can be determined more quickly than when measuring the 7-day strength or the 7-day strength of the material.
[0009] Furthermore, the formulation test method of the present invention involves increasing the amount of solidifying agent added according to the characteristic curve in the first addition amount determination step, and determining the amount of solidifying agent added (kg / m³). 3 It is preferable to define the threshold pH as the pH at which the rate of change of pH relative to ) transitions from a state where it exceeds 0.5% to a state where it becomes 0.5% or less.
[0010] This allows for the rapid determination of the optimal amount of solidifying agent to add to the ground material during the first application.
[0011] Furthermore, the present invention relates to a ground improvement method in which a solidifying agent is added to the ground material in two stages and mixed together.
[0012] A ground improvement method according to a first aspect of the present invention includes a first solidifying agent mixing step of adding the solidifying agent to the ground material and stirring and mixing it, and a second solidifying agent mixing step of further adding the solidifying agent to the ground material and stirring and mixing it, wherein the amount of the solidifying agent added in the first solidifying agent mixing step is the amount added in the first step determined by the test method of the present invention.
[0013] This allows for the optimal determination of the amount of solidifying agent to be added to the ground material in the first stage, thereby achieving greater unconfined compressive strength.
[0014] Furthermore, the ground improvement method in the second aspect of the present invention includes a first solidifying agent mixing step of adding the solidifying agent to the ground material and stirring and mixing it, and a second solidifying agent mixing step of further adding the solidifying agent to the ground material and stirring and mixing it, wherein in the first solidifying agent mixing step, after stirring and mixing the ground material and the solidifying agent, the pH of the mixed soil of the ground material and the solidifying agent is measured, and based on the characteristic curve created by the mixing test method of the present invention, the process proceeds to the second solidifying agent mixing step on the condition that the pH of the mixed soil exceeds the threshold when the amount of solidifying agent added is increased according to the characteristic curve.
[0015] This makes it possible to determine the optimal amount of solidifying agent to add to the ground material in the first stage, even if the ground environment at the work site changes and deviates from the results of the prior mix design test. [Brief explanation of the drawing]
[0016] [Figure 1] A plot showing the relationship between the amount of solidifying agent added to the ground material and the pH of the soil mixture of the ground material and the solidifying agent. [Modes for carrying out the invention]
[0017] The present invention will be described in more detail. Note that, unless otherwise specified, the "~" in a numerical range represents "from... to...", including both of the numerical values at both ends. Also, when indicating a numerical range, the upper limit value and the lower limit value can be appropriately combined, and the resulting numerical range is also considered to be disclosed.
[0018] The ground material used in the present invention is not particularly limited, and examples thereof include humus soil, peat, clayey soil, peat soil, silt soil, and loam soil.
[0019] Examples of the solidifying agent used in the present invention include quicklime, slaked lime, cement, or a cement-based solidifying agent. Two or more of these can be used in combination. Examples of cement include Portland cement, blast furnace cement, etc. Examples of the cement-based solidifying agent include ettringite-based, particularly the mixed type, as well as the calcined finely pulverized type.
[0020] [Measurement Step] In the method for mixing the solidifying agent in the mixing test method of the present invention, a normal method can be appropriately used, and examples thereof include manual stirring and stirring and mixing using a stirring mixer. The solidifying agent can be added as a powder or as a mixed slurry with water, etc.
[0021] The mixing test method of the present invention measures the pH of the mixed soil of the ground material and the solidifying agent or the suspension of the mixed soil. The method for measuring the pH is not particularly limited, and examples thereof include the indicator method, the metal electrode method, the glass electrode method, and the semiconductor sensor method. The suspension of the mixed soil is prepared by adding water such that the mass ratio of water (including the water in the mixed soil) to the dry mass of the mixed soil becomes 5, based on JGS 0211-2009 "Test Method for pH of Soil Suspension". Note that the pH measurement may be performed while gradually adding the solidifying agent to the ground material.
[0022] [First Addition Amount Determination Step] Based on the measurement results obtained by measuring the pH of the soil mixture of the ground material and the solidifying agent, or the suspension of said soil mixture, the amount of solidifying agent to be added is determined as the first addition amount, which corresponds to the point where the pH changes from below a predetermined threshold to above a predetermined threshold when the amount of solidifying agent added is increased according to a characteristic curve representing the correlation between the amount of solidifying agent added to the ground material and the pH of the soil mixture. The threshold pH range is 10.5 to 12.5, preferably 11 to 12.5, and more preferably 11.5 to 12.
[0023] Here, when the amount of solidifying agent added is increased according to the characteristic curve, the amount of solidifying agent added (kg / m³) 3 The threshold pH may be defined as the pH at which the rate of change of pH relative to ) transitions from a state where it exceeds 0.5% to a state where it falls below 0.5%. If the rate of change of pH is expressed as [pH / amount of solidifying agent added], the threshold pH is 5.0 × 10⁻⁶. -3 (m 3 This corresponds to ( / kg). Furthermore, the threshold can be pre-set based on past performance or simulations.
[0024] If the number of plots is insufficient and the threshold cannot be determined, the soil mixture preparation and pH measurement will be repeated. Since the test method of the present invention consists only of preparing the soil mixture and measuring the pH of the soil mixture, it can be repeated multiple times in one day.
[0025] Alternatively, the rate of change in pH may be determined by differentiating the approximate formula of the obtained characteristic curve and finding the slope of the characteristic curve (the amount of change in pH with respect to the amount of solidifying agent added). Examples of approximate formulas for the characteristic curve include logarithmic functions and exponential functions. In this case, since the characteristic curve may also change depending on the number of plots, it is preferable to have at least four plots. If there are not enough plots and the amount of the first addition cannot be determined, the soil mixture and pH measurement should be repeated.
[0026] Furthermore, in humus and organic soils, the reason why the ground material inhibits the solidification of the solidifying agent is that dissolved calcium ions react with reactants (humic acid and fulvic acid) contained in the ground material to produce calcium salts, which then cover the surface of unhydrated cement particles. The reason why adding the solidifying agent in two stages results in a greater final unconfined compressive strength of the ground than mixing the entire amount at once is that the reaction is initiated first with the first addition of the solidifying agent until the reactants are eliminated, thereby maximizing the capacity of the solidifying agent when it is added in the second stage.
[0027] Once the reaction producing the calcium salt described above is complete and the reactants are gone, the pH of the ground material reaches approximately the same level as the pH of the solidifying agent alone. Therefore, by setting the amount of solidifying agent added in the first addition to the point where the pH shifts from below a threshold within the range of 10.5 to 12.5 to exceeding that threshold, the reactants that hinder the solidification of the ground material can be efficiently removed.
[0028] Although the mixing test method of the present invention is usually performed in a laboratory beforehand, it may also be performed at the work site. Since it does not take time to prepare the mixed soil and measure the pH of the mixed soil, the amount of the first solidification agent to be added can be determined quickly.
[0029] [Soil improvement method] The ground improvement method of the present invention includes a first solidifying agent mixing step and a second solidifying agent mixing step.
[0030] [First solidifying material mixing process] The first solidifying agent mixing step is a process in which a solidifying agent is added to the ground material and mixed by stirring to create the first mixed soil. The amount of solidifying agent to be added in the first solidifying agent mixing step is determined by the aforementioned test.
[0031] Furthermore, according to another aspect of the present invention, in the first solidifying agent mixing step, the ground material and the solidifying agent may be stirred and mixed, and the pH of the mixed soil of the ground material and the solidifying agent may be measured. Based on the characteristic curve created by the aforementioned mix design test, the process may proceed to the second solidifying agent mixing step only if the pH of the mixed soil exceeds a predetermined threshold. The pH may be measured directly on the mixed soil or on a portion of the recovered mixed soil.
[0032] [Second solidifying material mixing process] The second solidification agent mixing process involves adding a solidification agent to the ground material and mixing it to create the second mixed soil.
[0033] The amount of solidifying agent to be added in the second solidifying agent mixing process is determined by a separate mix design test. Specifically, after stirring and mixing the ground material and the solidifying agent, the unconfined compressive strength of the mixed soil is measured for each of several different amounts of solidifying agent added in the second stage of the solidifying agent addition. Based on the measurement results obtained, the total amount of solidifying agent to be added is determined from the relationship between the total amount of solidifying agent added and the unconfined compressive strength, and the amount of solidifying agent to be added in the second solidifying agent mixing process is determined.
[0034] The second solidifying agent mixing step may be performed immediately after the first solidifying agent mixing step, or an interval of 20 minutes to several days may be provided.
[0035] Furthermore, the first and second solidifying agents may be of the same type, or they may be of different types.
[0036] As aspects of the first addition and the second addition of the solidifying material in the ground improvement method of the present invention, they can be appropriately selected according to the actual improvement method using this. In the case of the deep mixing method, for the mixing method, the energy possessed by stirring blades, screw augers, compressed air, or high-pressure fluids can be utilized. Also, in the case of this deep mixing method, for example, the first addition can be performed when the stirring and mixing shaft penetrates, and the second addition can be performed when it is pulled out. In the case of surface layer mixing treatment, a stabilizer, a backhoe, etc. can be utilized. The solidifying material can be added as a powder or as a mixed slurry with water or the like.
Example
[0037] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. [Materials Used] (1) Ground material: Humus soil (2) Solidifying material: Cement-based solidifying material (Product name: GS225, manufactured by Taiheiyo Cement)
[0038] [Experiment 1: pH measurement test] The solidifying material was added to the ground material at ratios of 0, 50, 100, 150, 200, 300, 400, and 500 kg / m 3 and mixed with a mixing mixer. Then, the ground material and the solidifying material adhering to the stirring blades etc. were recovered, and further thoroughly mixed by hand to produce a mixed soil. The pH of this mixed soil was measured by the glass electrode method.
[0039] The measurement results of pH are shown in Table 1. Also, as shown in FIG. 1, a characteristic curve diagram showing the relationship between the addition amount of the solidifying material to the ground material and the pH of the mixed soil was created. As shown in FIG. 1, when the addition amount of the solidifying material is 50 kg / m 3 the pH of the mixed soil exceeds the preset threshold value of 10.5, and when the addition amount of the solidifying material is 150 kg / m 3 the pH reaches the upper limit, and it was found that even if the amount of the solidifying material is increased further, the pH of the mixed soil becomes constant. Also, in the mixed soil with the addition amount of the first solidifying material of 150 kg / m 3 the addition amount of the solidifying material (kg / m 3It was found that the pH change rate relative to ) transitions from a state where it exceeds 0.5% to a state where it falls below 0.5%.
[0040] [Table 1]
[0041] [Experiment 2: Solidification Test] As shown in Table 1, the first solidifying agent was added to the ground material and mixed in a mixing mixer to prepare the first mixed soil. The second solidifying agent was then added to the first mixed soil and mixed again in a mixing mixer to prepare the second mixed soil. Subsequently, cylindrical specimens of φ5 × 10 cm were prepared in accordance with JGS 0821-2009 "Preparation of specimens of stabilized soil without compaction". These specimens were sealed and cured at room temperature of 20°C and humidity of 90%, and the unconfined compressive strength was measured at 28 days in accordance with JIS A1216 "Unconfined compressive strength test method for soil".
[0042] [Table 2]
[0043] As shown in Table 2, compared to the comparative example, Examples 1-5 showed improved unconfined compressive strength of the improved ground. In particular, when the pH of the mixed soil was in the range of 10.5 to 12.5, and the amount of solidifying agent added (kg / m³) 3 The pH change rate relative to the solution transitioned from exceeding 0.5% to being 0.5% or less, when the amount of solidifying agent added in the first batch was 150 kg / m³. 3 In Example 3, the uniaxial compressive strength of the improved ground showed the maximum value. That is, the amount of the first solidifying agent added was such that the pH of the mixed soil was in the range of 10.5 to 12.5, and the amount of the solidifying agent added (kg / m³) 3 150 kg / m³ corresponds to the point where the rate of change in pH relative to ) transitions from a state where it exceeds 0.5% to a state where it falls below 0.5%. 3 Based on this, by performing stirring and mixing with varying amounts of the second solidifying agent, the optimal total amount of solidifying agent to be added for the desired uniaxial compressive strength of the improved ground can be determined.
[0044] From the above, in a ground improvement method in which the solidifying agent is added in two stages, a first solidifying agent addition stage and a second solidifying agent addition stage, when the amount of solidifying agent added is increased according to the characteristic curve created in the mix design test, the amount of solidifying agent added in the first stage corresponds to the point where the pH of the mixed soil of the ground material and solidifying agent transitions from a state where it is below a threshold of 10.5 to 12.5 to a state where it exceeds the threshold, thereby obtaining improved ground with the greatest improvement in unconfined compressive strength. In other words, when the amount of solidifying agent added is increased according to the characteristic curve created in the mix design test, the point where the pH of the mixed soil of the ground material and solidifying agent transitions from a state where it is below a threshold of 10.5 to 12.5 to a state where it exceeds the threshold can be determined, thereby minimizing the total amount of solidifying agent added to obtain improved ground with the required unconfined compressive strength.
[0045] It should be noted that the present invention is not limited to the above embodiments or examples, and it is clear that the scope of the present invention can be modified or altered to the extent that is obvious to those skilled in the art. It is also clear that the scope of the present invention is not limited to the above embodiments or examples, but also includes modified or altered versions thereof.
Claims
1. In a ground improvement method in which a solidifying agent is added to the ground material in two stages and mixed, a test method for determining the amount of the first solidifying agent to be added, A measurement step is performed in which the ground material and the solidifying agent are stirred and mixed, and the pH of the mixed soil of the ground material and the solidifying agent is measured for each of several different amounts of the solidifying agent added to the ground material. Based on the measurement results obtained in the measurement step, the first addition amount determination step determines the amount of solidifying agent to be added, which corresponds to the point at which the pH of the mixed soil transitions from being below a threshold within the range of 10.5 to 12.5 to exceeding the threshold when the amount of solidifying agent to be added to the ground material is increased according to a characteristic curve representing the correlation between the amount of solidifying agent added to the ground material and the pH of the mixed soil, as the first addition amount. A formulation test method, including the following.
2. In the aforementioned first step of determining the amount to be added, When the amount of solidifying agent added is increased according to the characteristic curve, the amount of solidifying agent added (kg / m³) ３ The formulation test method according to claim 1, wherein the threshold pH is defined as the pH at which the rate of change of pH relative to ) transitions from a state in which it exceeds 0.5% to a state in which it becomes 0.5% or less.
3. In a ground improvement method in which a solidifying agent is added to the ground material in two stages and mixed, A first solidification material mixing step involves adding the solidification material to the ground material and stirring and mixing it, The process includes a second solidification material mixing step in which the solidification material is further added to the ground material and stirred and mixed, The amount of solidifying agent added in the first solidifying agent mixing step is the first amount added, determined by the test method described in claim 1. A ground improvement method characterized by the following features.
4. In a ground improvement method in which a solidifying agent is added to the ground material in two stages and mixed, A first solidification material mixing step involves adding the solidification material to the ground material and stirring and mixing it, The process includes a second solidification material mixing step in which the solidification material is further added to the ground material and stirred and mixed, In the first solidification agent mixing step, the ground material and the solidification agent are stirred and mixed, and then the pH of the mixed soil of the ground material and the solidification agent is measured. Based on the characteristic curve created by the mix design test method according to claim 1 or 2, the procedure proceeds to the second solidifying agent mixing step, provided that the pH of the mixed soil exceeds the threshold. A ground improvement method characterized by the following features.